(1) Technical Field
This invention pertains to unions and pertains particularly to a union which may be utilized in a tree cap connectable on a production wellhead.
(2) Description of the Related Art
Many forms of unions or couplings are shown in the 38th revision 1988-89, "COMPOSITE CATALOG OF OIL FIELD EQUIPMENT AND SERVICES", published by Gulf Publishing Company, P.O. Box 2608, Houston, TX 77252. An example of a coupling utilizing a metal seal ring is shown on page 3327 of volume 3 of the previously mentioned publication. On page 3349, also in volume 3, are shown various forms of christmas tree caps utilizing metal seal rings. Also in volume 3, on page 4051, is shown a tree cap having a resilient seal and metal seal surfaces for sealing. Pages 2206 and 2207 of volume 2 depict various forms of unions utilizing metal seal surfaces, metal seal surfaces with resilient seals or resilient seals alone for sealing. The form of FIGURE 600 on page 2206 shows a union having a separate bronze seat insert ring for additional pressure sealing capability.